1. Field of the Invention
The present invention generally concerns digital electronic cameras, and waterproof housings for cameras including digital electronic cameras.
The present invention particularly concerns (i) digital electronic cameras encapsulated in plastic, with no seals or penetrating pins, wires or other objects whatsoever, (ii) digital electronic cameras so encapsulated with no air or other gas whatsoever inside, (iii) digital electronic cameras with water-immersed adjustable optics, and (iv) the communication of information, electrical power and control across a watertight barrier particularly as may encapsulate and protect a digital electronic camera.
2. Description of the Prior Art
2.1 Relevant Previous Patents
A significant body of prior art concerning waterproof housings for conventional film cameras is substantially irrelevant to the present invention for several reasons. First, the housing or case for a conventional, non-electronic, camera must open for retrieval and replacement of the film—as will prove to be unnecessary with a digital electronic camera. Second, since the camera's case or housing will open, and required replacement of batteries is readily accomplished by physical substitution, no battery recharging need transpire through the case or housing.
The case and its waterproof seals can be, and often are, quite sophisticated in supporting the transmission of mechanical forces and adjustments as may attend, inter alia, adjustment of the camera's focus and/or the actuation of its shutter. However, and although a digital electronic camera may have a focus adjustment and will have a shutter, these mechanisms can be electrically, as opposed to mechanically, actuated.
Accordingly, the present invention will prove more analogous to certain prior art underwater electronic devices—including electronic imaging devices such as, inter alia, a video tape recorder—than to underwater film cameras. (Of course, even with a video tape recorder, a watertight enclosure will open for access to the videotape.)
In this regard, U.S. Pat. No. 3,952,190 to Perkins for an UNDERWATER STROBE FLASH UNIT concerns a method of waterproofing a strobe flash unit for use in underwater photography. A mold is formed and a strobe flash unit is mounted within the mold. Epoxy resin is poured into the mold to surround the strobe flash unit with the resin. The resin is then cured until it hardens, at which time the mold is removed from the epoxy resin and strobe flash unit. The resultant product is a strobe flash unit encapsulated in a transparent waterproof casing. Such encapsulation will be seen to be suitably employed in the present invention.
As regards the communication of power to handheld underwater electronic imaging devices, U.S. Pat. No. 4,009,419 to Ligman for a SAFETY CIRCUIT FOR VIDEO DIVER concerns an underwater diver who is provided with a video camera, light, and communications all of which is supplied with electrical current from the surface by a shipboard electrical circuit. The diver is protected from accidental excessive voltages and current by magnetically isolating the diver's current from the shipboard current and by employing optical feedback to control the voltages for the diver. Additionally, a standby battery is employed to energize this equipment when the shipboard power fails. The entire shipboard power supply is contained in a waterproof box upon which is also mounted a video monitor and a video recorder, both secured in watertight fashion to the box. The present invention will be seen to involve the transmission of power into a waterproof enclosure, but not while the enclosure is immersed, and normally not while an electronic digital camera within the enclosure is in use.
The present invention will be seen to involve optical data transmission. U.S. Pat. No. 5,847,753 to Gabello, et al., for a CAMERA SYSTEM FOR SCANNING A MOVING SURFACE concerns a camera system utilizing a line scan (linear array) camera designed to scan a moving surface and subsequently to generate and to transmit a high quality digitized video signal over a long a distance by an optical fiber. The primary function of the system is: to scan a moving surface using a 2048 or a 1024 linear array; to condition and digitize the array analog video signal; and subsequently to transmit to a computer processing unit, without a noticeable loss in fidelity, the digitized video data over a long distance by means of an optical fiber connected to the camera and the computer processing unit. The system also functions to transmit both video signals and non-video information signals over a fiber optic link from the camera to the computer processing unit.
2.2 An Exemplary Modification of an Existing Digital Camera
The present invention will be seen to employ but very, very slight—substantially inconsequential—physical and electrical modifications to an existing digital electronic camera. No modifications at all are required by the present invention in the personal computer, nor in the operating software, that are commonly used to recover digital images from the digital electronic camera. However, all these things are readily susceptible of modification, if required.
It is thus useful to consider the susceptibility of a digital electronic camera to electrical and/or physical modification. An example of modifications—much more extensive than are required by the present invention—to an existing digital camera to support of its use in a non-standard, space borne, environment is shown in a Stanford University student project reported on the World Wide Web at <http://maverick.stanford.edu/.about.ssdl . . . System/payload/camera>.
2.2.1 An Exemplary Existing Digital Electronic Camera
The Logitech Fotoman Plus digital electronic camera is a 8-bit grayscale digital camera, capable of storing 32 JPEG compressed pictures in memory. Its specifications, according to Logitech, are as follows:
The camera dimensions are 16.8 centimeters (6.7 inches) by 8.1 cm (3.2 in) by 3 cm (1.2 in). The camera weight is 284 grams (10 ounces).
Camera image quality is 256 gray levels over 496.times.360 pixels, for an equivalent resolution of 120 dots per inch (120 dpi) over a photo approximately 4 in (12.7 cm) wide.times.3 in (8.9 cm) high.
The lens is fixed focus with a 8.5 millimeters (mm) focal length, f/4.5. The 35 mm camera equivalent focal length is 64 mm. Shooting range is 3 feet (1 meter) to infinity.
The camera's equivalent film sensitivity is approximately ASA 200 without the neutral density filter, and approximately ASA 25 with the filter.
The camera's electronic shutter speed is 40 milliseconds (.about. 1/30) with the flash, and 0.5 to 50 msec ( 1/2000 to 1/20) without the flash.
The flash guide number equivalent is 27 at ASA 200. The flash shooting range 3 ft (1 m) to 8 ft (2.5 m). The life of the flash is 10,000 flashes.
The image capacity of camera is 32 pictures in an image storage medium: namely, solid state (dram) memory with battery backup.
The image sensor type is a CCD (charge-coupled device). The raw image size is 179 kb (8 bits per pixel). Compressed image size varies with the image. Average compressed image size is 23 kb with 8:1 compression using the JPEG image compression method.
The adapter rings have a small end of 27 mm threaded outer diameter, and a large end of 37 mm threaded inner diameter.
The camera cable length is 6 ft. (2 m) of cable suitable for the camera's RS423 serial interface (which is simply 5 v version of the more universal RS232 serial interface, which will be seen to be the type used in the preferred embodiment of the present invention).
The baud rate of the interface is 9.6 K baud receive, and 9.6K, 19.2K, 38.4K, 57.6K, of 115 k baud transmit.
The main power source of the camera is two rechargeable nickel-cadmium batteries, AA size, 600 ma, 1.2 V. The time needed to charge these Ni-Cad batteries is 6 hours minimum. In estimating loss of charge in the Ni-Cad batteries assume that, at room temperature, the batteries lose about 20% of a full charge every time the camera takes one full load of photos (32 photos). The batteries lose about 15% of a full charge every time the camera goes 24 hours without recharging.
The battery charger has an output 12 vdc v, −2 v, 500 mah minimum. The polarity-positive pole is at center.
A memory power source is based on a 3 v lithium cell.
Camera operating temperature and humidity is 0 to 40.degree. C. at 95% humidity or less. Camera storage temperature and humidity is −40 to 50.degree. C. at 95% humidity or less.
An existing Logitech Fotoman Plus digital camera (the “Fotoman camera”) is modified by, among other things, placing it in a protective box. The capabilities of this digital camera include JPEG image compression, storage in DRAM of up to 32 496.times.360 images with 8-bit gray scale in compressed form. The compression results in a JPEG image size of about 23 Kb.
A serial link to the CPU, RS-232, is used to load into the Fotoman camera memory its operating software, to give it instructions, and to transfer back the camera status and full images.
The digital camera can be powered on/off, from the V bus of the spacecraft. A voltage regulator and a bypass capacitor are used to replace the Ni-Cad batteries normally used to power the Fotoman Plus (see schematic) A lithium battery, used by the Fotoman to maintain the operating software in memory, is left in the camera.
2.2.2 Exemplary Previous Electrical Modifications to an Existing Digital Electronic Camera
In accordance with the present invention, connection will be made to the circuitry of a digital electronic camera. That a connection to—and more, rising to the level of actual modification of—the circuitry of an existing digital electronic camera might be made is known.
For example, the aforementioned Fotoman Plus digital electronic camera was subjected to electronic modifications. The Fotoman Plus camera was already designed with appropriate digital communications interfaces without the need for any custom adapter. However, an external switch controlled by the on/off command from the CPU and voltage regulation had to be added. It was so added by wiring an existing RS423 serial interface from a bottom 6 electrodes already present in the camera. (With the lens on top, the six electrodes from left to right are: 1. Connection directly to the battery through a fuse, located in the camera, which is used to monitor battery level in manufacturing. A battery eliminator could be connected, but the fuse would have to be bypassed; 2. RS423 out; 3. Charge in (V); 4. RS423 in; 5. Ground, used for both power and RS423; and 6. Unused.)
Next, a power regulation and switching circuit were designed to turn on the Fotoman camera if a “on” signal was received from the CPU through the bus of the space satellite in which the modified camera was to be flown, and contained.
Finally, the flash had to be selectively electronically disabled by removing certain components off the PCB. (The components were C32, Q18, Q24, Q27, R94, and R93, as indicated on the printed circuit board of the camera.) 2.2.3 Exemplary Modifications to the Software-Based Interface and Control of an Existing Digital Electronic Camera
It will be seen to be one of the strengths of the present invention that no modification is needed to the firmware within the camera, nor the software within a connecting computer. It will be understood, however, that such minor modifications as might be required are well within the skills of a practitioner of the digital computer programming arts.
For example, the Photoman Plus camera has a command set the detail nature of which is not of particular concern in the present application.
Using this instruction set software for control of the camera was modified in accordance with the space mission of the camera.
The Fotoman Plus camera software architecture is based on a boot code stored in the Fotoman Plus camera ROM. This main code stored in the Fotoman Plus camera RAM is known as FOTOWARE. This code operates the Fotoman Plus camera, performs the data compression, and manages the communications with an external computer through a serial link.
The Fotoman Plus camera software architecture is also based on an exploitation code, known as FOTOTOUCH, based on an external computer. This code contains a dialogue/acquisition segment, an executable named FOTOMAN.EXE, and an image processing segment.
Finally, the Fotoman Plus camera software architecture is also based a native mode communication program TERM permitting ASCII commands—used in commanding the Fotoman Plus camera—to be entered via a keyboard.
The camera modification plan called for a special version of the FOTOWARE that permitted programmed (i) disabling of the flash, (ii) manual setting of the exposure time, and (iii) control of the battery counter. The battery counter is a model of the battery maintained by the FOTOWARE, which does not measure any physical quantity from the batteries. However, the battery counter must be above a certain level, before the Fotoman can take a picture.
However, if the camera batteries are removed and replaced, the onboard software assumes that the replacement batteries are uncharged. As the power circuitry for the digital camera replaces the batteries, on power up, the counter will read zero and the camera will not be able to take a picture. By controlling the counter, the programmer(s) can change the erroneous indication of insufficient power, and can take a picture immediately. Flash control is recommended, as the flash will be physically disabled.
FOTOTOUCH or any other standard image manipulation package can be used in the ground station to view and process the images, which are downloaded in standard JPEG format.
2.2.4 Exemplary Use of a Modified Existing Digital Electronic Camera
The present invention deals with a digital electronic camera modified for underwater use. It is known to attempt to modify a digital electronic camera for a specific applications environment, to wit: the space borne application of the Fotoman Plus camera.
In that application full new software supports camera dialogue/acquisition with the spacecraft CPU, and interfaces the cameral into the main control module of the spacecraft. This software performs the following tasks: 1. turning on and off the Fotoman Plus; 2. uploading FOTOWARE from the PROM into the Fotoman Plus RAM at a given time; 3. sending orders to take pictures to the Fotoman; 4. Request and receiving status, contact, and image inventory information; and 5. retrieving pictures from the Fotoman, to be stored in the CPU, which will be sent at a later time to the ground station.
These tasks can be performed using the 16 commands set of provided in the Native Mode Toolkit.
Typical tasks for the modified FotoMan executable under software control are to 1. take a picture at a given time (using the on-board clock); and 2. download a picture #n stored in CPU memory.
For further explanation see the Fotoman Plus camera User's Guide (a basic user's guide) and the Fotoman Plus Camera Native Mode Toolkit (logical interface specifications) supplied by Logitech Inc., Fremont Calif. 94555. See also JPEG documentation and source code at ftp site: <ftp.uu.net/graphics/jpeg file jpegsrc.v4.tar.Z>; and general information on image compression from the list at FAQ of the Internet newsgroup at <http://comp.compression.research>.